Method of casting clad



March 1, 1966 J. L. MA

METHOD OF CASTING CLAD 2 Sheets-Sheet 1 Filed Jan. '7, 1965 INVENToR.James L. M61 Y J. L. MA- 3,237,298

ING CLAD 2 Sheets-Sheet 2 March l, 1966 Filed Jan. v, 1965 Iliff. 5. f

ATTORNEYS.

United States Patent O 3,237,298 METHOD OF CASTING CLAD .lames L. Ma,West Chester, Pa., assignor to Lukens Steel Company, Coatesville, Pa., acorporation of Pennsylvania Filed Jan. 7, 1965, Ser. No. 424,463 5Claims. (Cl. 29-528) This invention relates toa method of casting clad.Such clad usually comprises a low carbon steel layer or alloys thereofand a stainless steel layer bonded thereto by casting and rollingoperations. The meth-d accordingly is directed to the production oflaminated -steel sheets, strips, bars or slabs. In addition to a carbonsteel backing plate assemblies include metal inserts composed ofstainless steel, nickel, Monel metal, Inconel metal, titanium,zirconium, alloys of the foregoing and other metals generally used inthe -steel clad industry.

An object of the invention is to reduce the labor involved in thecladding of metals by reducing the number of steps incident to theproduction of clad metal.

A further object is to provide a method which includes the casting of abase metal, such as low carbon steel or its alloys, in a mold about apair of inserts which are separated from each other by a partingcomposition as hereinafter more particularly described.

This application is a continuation-in-part of my application Serial No.129,110, filed August 3, 1961, which is a continuation-in-part rofapplication Serial No. 736,814, tiled May 21, 1958, Patent No. 2,995,816of August 15,

Referring to the drawings:

FIGURE 1 shows a vertical section through the insert assembly ready forinsertion into a mold;

FIGURE 2 shows a vertical section through the mold and the insertlocated therein;

FIGURE 3 is a vertical section similar to FIGURE 2 after the moltenmetal forming the backing material has been poured.

FIGURE 4 is a top plan View of a mold illustrating the insertssupporting elements; and

FIGURE 5 is a vertical section taken substantially along the lines V-Vof FIGURE 4.

A typical apparatus for carrying out the steps of the process is thatshown in the several figures of the drawings :wherein the insert or pack2 is prepared by placing, after cleaning, a pair of cladding sheets,strips, bars or slabs 4 in juxtaposed position with a layer of partingmaterial between the saine.

According to the invention, the assembly 2 may be quickly dipped into abath of molten metal, such as molten steel to provide the layerindicated by reference numeral 8. After cooling, the assembly isconditioned by sand or grit blasting, following which the assembly isplaced in a mold 10. Molten base metal such as low carbon alloy steel ispoured into the mold after the insert assembly has been placed in themold and held in the position shown in FIGURE 2 by suitable supports asdisclosed, for instance, by Patents Nos. 1,868,749 and 1,967,754 toIngersoll. Other suitable means of support may be substituted for thesupports shown in these patents.

As noted above, the molten base metal forming the 3,237,298 PatentedMar. 1, 1966 "ice backing layers, is poured into the mold to fill thesame as indicated in FIGURE 3.

The molten metal and inserts are cast together to form two cast cladmetal plates, the parting compound 6 permitting separation of the cast`clad metal plates from each other. Should some of the backing materialrequire removal, such as material which lies below the insert as Ishownin FIGURE 3, such material `can be removed by conventional methods.

After the cast clad plates have been removed from the mold, they areseparated to form two cast clad metal plates, each having a base layer12 and an insert 4 bondedV thereto. Each of them is subsequently rolledby the use of heat and pressure into clad plates at a ratio of 15 to 1or t-hinner. Alternately, the entire cast clad assembly may be rolledbefore separation.

During the casting and rolling operations, the composite metal platesare subjected to high heat and heavy pressure, in which heats of 2100 F.and higher are used while the rolling pressure is such as to reduce thecompound metal bodies thinner than the conventional l() to 1 ratio orabout 15 to 1 or even below the 15 to l ratio of reduction.

The present invention is also directed to a parting cornposition that isan important factor in the process iwhich composition prevents sticking`or welding of the cladding inserts during the casting and rolling ofthe cast clad ingot.

Prior to placing the inserts with their faces in juxtaposed postion, oneor both of the juxtaposed fa-ces are coated with a primary coating of aparting composition, and is later coated with a covering or finalcoating of the parting composition, both being defined hereinafter. Boththe primary and iinal coatings include a binding agent of especialsignificance. This binding agent consists of about 1% to 5% by weight,preferably 1% to 2% by weight, of nitrocellulose dissolved in ethylacetate. In the examples the preferred binding agent is used.

The signic-ant difference of this binder as distinguished from otherknown binders is that it contains a much higher viscositynitrocellulose. Because of its very high viscosity, the binder canabsorb more refractory oxides, thus giving greater protection to thesurfaces of the inserts during the casting and rolling operations. Theparting composition contains a high viscosity binder with a ratio ofrefractory oxide to binders of about 0.5-4z1, preferably 1-3:1 -ofchromium oxide in the prime coat or manganese oxide in the covering coatbased on the weight of the binder disclosed above. The ratios andpercentages herein are based on weight. The refractory oxides should besized to pass a 200 mesh screen.

It is of particular importance to provide a binder that can absorb morerefractory oxides, since the inserts are subjected to the high pouringtemperature of the carbon steel, and the cast clad insert issubsequently rolled into clad plates at the high ratio of 15 to 1 orthinner.

Heretofore, in the use of separating compounds containing refractoryoxides, the maximum 4-ply clad sandwich assemblies were reduced only 10to 1, and the maximum amount -of refractory oxide could not exceed about1-11/2 times the weight of the binder without causing precipitation orbecoming lumpy. The amount of oxide used in the improved binder can beas high as three to four times the weight of the binder.

The following parting compositions have been used to achieve theimproved results during casting and rolling operations wherein claddinginserts are cast with a molten base metal in molds, and after removaltherefrom, are reduced by rolling to as high as a to l ratio or thinner:

Prime Coat Covering Coat Parts Parts I. Chromic oxido 200 15 Manganesedioxide 30 mesh 200 mesh).

High viscosity binder. 13. l I-Iigh viscosity binder- 10. 4

Total 28. l Total 40. 4

II. Chromie oxide 200 15 Manganese dioxide 30 mes A 200 mesh).

High viscosity binder- 12 High viscosity binder 10. 5

Total 27 Total 40. 5

III. Chromic oxide 200 32. 7 Manganese dioxide 56. 8

mesh. 200 mesh).

High viscosity binder- 22 High viscosity binder- 22 Total 54. 7 Total78.8

IV. Chromie oxide 22 Manganese dioxide 60 20Q mesh). 20U mesh).

High viscosity binder. 22 High viscosity binder- 22 Total 44 Total 82 V.Chromie oxide 35 Manganese dioxide i 40 20Q mesh). 200 mesh).

High viscosity binder. 9 High viscosity binder l1 Total 44 Total 55 Theparting composition noted under III is the preferred composition, bothas primary and secondary or covering coat,

The high viscosity binder consists of a high viscosity nitrocellulosehaving a viscosi-ty of about 100-200 seconds, preferably about 125seconds, at 77 F. as measured by the falling ball method. The gradespecification of nitrocellulose is normally given in terms of theviscosity of the nitrocellulose when dissolved in a standard solventmixture. This test consists of falling a standard fivesixteenth of aninch steel ball through a ten inch column of nitrocellulose solution ina standard glass cylinder of one inch diameter. The results areexpressed as time of all in seconds. In the previously used bindersdissolved in ethyl acetate, the rate of fall, i.e. the viscosity number,rarely exceeds one second.

A particularly effective parting compound for high temperatureapplications of casting and rolling clad consists of using chromic oxidemixed with a high viscosity binder, followed by a covering coat ofmanganese oxide mixed with a high viscosity binding agent. It appearsthat the manganese dioxide acts as an oxidizer for metallic chromiumwhich can be formed from the chromic oxide under the reducing atmospheregenerally existing in the insert assembly. Other refractory oxides areless preferred.

The parting composition disclosed herein nds particular application inthe casting and rolling of clad metal assemblies. It will be appreciatedthat other uses for the composition will occur to one skilled in theart.

The above description and drawings disclose one embodiment of theinvention, and specic language has been employed in describing thefigures. It will, nevertheless, be understood that no limitations of thescope of the invention are thereby contemplated, and that variousalterations and modifications may be made as would occur to one skilledin the art to which the invention relates.

Iclaim:

-ll. A parting composition comprising a refractory oxide and a highviscosity binder wherein the ratio of refractory oxide to binder isabout l-3zl by weight, said high viscosity binder solution being l-5percent by weight nitrocellulose dissolved in ethyl acetate wherein thenitrocellulose employed has `a viscosity of about -200 seconds asmeasured by the falling ball method in a standard solution of 25% ethylalcohol, 55% toluene, and 20% ethyl acetate.

2. The composition of claim 1 wherein the binder is l-2 percentnitrocellulose dissolved in ethyl acetate.

A3. The composition of claim 1 wherein the refractory oxide is selectedfrom the group consisting of chromic oxide and manganese dioxide.

4. The method of casting clad metal which comprises placing a prime coatand a covering coat of a parting composition on`the opposing surfaces ofa pair of inserts, comprising a high viscosity binder and a refractoryoxide, said high viscosity binder being a l-5 solution by weightnitrocellulose dissolved in ethyl acetate wherein said nitrocelluloseemployed has a viscosity of about 1GO-200 seconds as measured by thefalling ball method in a standard solution of 25% ethyl alcohol, 55%toluene and 20% ethyl acetate, said priime coat having chromic oxide andsaid covering coat having manganese dioxide, assembling said insertsinto a pack, quick dipping said pack in a bath of molten steel to coverand seal the pack, placing said pack in a mold and casting the clad bypouring molten metal into the mold around said pack, removing the castclad from the mold and subjecting same to a rolling step with heat andpressure.

5. The process of claim 4 'wherein the cast -clad is rolled thinner thana ratio of l0 to l.

References Cited bythe Examiner UNITED STATES PATENTS 1,967,754 7/1934Ingersoll 29-527 XR 2,109,010 2/ 1938 Ingersoll 29-470.9 2,711,9666/1955 Watson et al 106-183 WHITMORE A. WILZ, Primary Examiner,

J. C. HQLMAN, Examiner,

1. A PARTING COMPOSITION COMPRISIING A REFRACTORY OXIDE AND A HIGHVISCOSITY BINDER WHEREIN THE RATIO OF REFRACTORY OXIDE TO BINDER ISABOUT 1-3:1 BY WEIGHT, SAID HIGH VISCOSITY BINDER SOLUTION BEING 1-5PERCENT BY WEIGHT NITROCELLULOSE DISSOLVED IN ETHYL ACETATE WHEREIN THENITROCELLULOSE EMPLOYED HAS A VISCOSITY OF ABOUT 100-200 SECONDS ASMEASURED BY THE FALLING BALL METHOD IN A STANDARD SOLUTION OF 25% ETHYLALCHOL, 55% TOLUENE, AND 20% ETHYL ACETATE.
 4. THE METHOD OF CASTINGCLAD METAL WHICH COMPRISES PLACING A PRIME COAT AND A COVERING COAT OF APARTING COMPOSITION ON THE OPPOSING SURFACES OF A PAIR OF INSERTS,COMPRISING A HIGH VISCOSITY BINDER AND A REFRACTORY OXIDE, SAID HIGHVISCOSITY BINDER BEING A 1-5% SOLUTION BY WEIGHT NITROCELLULOSEDISSOLVED IN ETHYL ACETATE WHEREIN SAID NITROCELLULOSE EMPLOYED HASVISCOSITY OF ABOUT 100-200 SECONDS AS MEASURED BY THE FALLING BALLMETHOD IN A STANDARD SOLUTION OF 25% ETHYL ALCOHOL, 55% TOLUENE AND 20%ETHYL ACETATE, SAID PRIME COAT HAVING CHROMIC OXIDE AND SAID COVERINGCOAT HAVING MANGANESE DIOXIDE, ASSEMBLING SAID INSERTS INTO A PACK,QUICK DIPPING SAID PACK IN A BATH OF MOLTEN STEEL TO COVER AND SEAL THEPACK, PLACING SAID PACK IN A MOLD AND CASTING THE CLAD BY POURING MOLTENMETAL INTO THE MOLD AROUND SAID PACK, REMOVING THE CAST CLAD FROM THEMOLD AND SUBJECTING SAME TO A ROLLING STEP WITH HEAT AND PRESSURE.